Internet Protocol (IP) multicast refers to that in an IP network, a data packet is sent to a certain determined node subset in the network by using a best-effort scheme, and the node subset is referred to as a multicast group. A source host sends only one piece of data, a destination address in the piece of data is a multicast group address, all receivers in the multicast group may receive the same data copy, and only hosts in the multicast group may receive the data, while other hosts outside the multicast group cannot receive the data.
In dependence on a virtual dedicated communication network established in a public network by an Internet service provider (ISP) and a network service provider (NSP), a VPN may divide an existing IP network into logically isolated networks.
The VPN is formed of a customer edge (CE), a provider edge (PE), and a provider (P, namely, a service provider network backbone router). The CE is directly connected to a service provider (SP) network, exclusively belongs to a certain VPN, only serves the exclusive VPN, and only maintains a set of forwarding mechanism, and the CE may be a router or a switch, and may also be a host; the PE is directly connected to the CE, is also connected to a public network and a VPN network, and serves a plurality of VPNs simultaneously; and the P is not directly connected to the CE. The PE and the P are managed only by the SP, and the CE is managed only by a user, unless the customer entrusts the SP with the management right. A PE may be connected to a plurality of CEs, and a CE may also be connected to a plurality of PEs belonging to the same SP or different SPs. On the PE, information of each network must be strictly distinguished, and a set of forwarding mechanism is independently maintained for each network. A set of software/hardware apparatus serving the same network on the PE is collectively referred to as an instance, a plurality of instances may exist simultaneously on the PE, and the same instance may be distributed on a plurality of PEs.
A multicast VPN solution needs to support a multicast function in an SP backbone network (a core network or a public network), and multicast data and a control message in a private network instance are transferred to a remote site of the VPN through a public network. A multicast instance operated in a VPN instance on a PE router is referred to as a private network multicast instance, and a multicast instance operated by a public network part of the PE router is referred to as a public network multicast instance. The public network multicast instance does not need to learn multicast data transferred in the private network, the private network multicast instance does not either need to learn multicast routing information in the public network instance, and private network multicast instances are isolated from each other.
If a VPN user needs to receive multicast data of other VPN users, a multicast VPN extranet networking solution may be used. The networking solution may be that, a source PE configures a receiver VPN multicast instance, and a Share-Group address of a receiver VPN is added to a newly configured receiver VPN multicast instance, a multicast tunnel from the newly configured receiver VPN multicast instance to the original receiver VPN multicast instance is established, and the original receiver VPN multicast instance and the newly configured receiver VPN multicast instance may communicate in an intranet manner; while on the source PE equipment, the newly configured receiver VPN multicast instance and the source VPN multicast instance realize an extranet in a local intersection manner, that is, communicate through an internal message between different VPN multicast instances on the same equipment, so as to complete the transfer of a Protocol Independent Multicast (PIM) protocol message and a multicast data message. A networking solution in the prior art may also be that, a receiver PE configures a source VPN multicast instance, a Share-Group address of an original source VPN is added to a newly configured source VPN multicast instance, a multicast tunnel from the newly configured source VPN multicast instance to the original source VPN multicast instance is established, and the newly configured source VPN multicast instance and the original source VPN multicast instance may communicate in an intranet manner; while on the receiver PE equipment, the newly configured source VPN multicast instance and the receiver VPN multicast instance realize an extranet in a local intersection manner, that is, communicate through an internal message between different VPN multicast instances on the same equipment, so as to complete the transfer of a PIM protocol message and a multicast data message.
In the implementation of the present invention, the inventor finds that at least the following problems exist in the prior art:
In the prior art, no matter whether the source PE configures the receiver VPN multicast instance, or the receiver PE configures the source VPN multicast instance, the multicast VPN extranet is realized through local private network intersection, and a multicast stream of a remote VPN site still uses a multicast tunnel of the same VPN. If the receiver VPN multicast instance needs to receive multicast data from a plurality of different source VPNs, the receiver PE needs to additionally configure a plurality of source VPN multicast instances, while the receiver PE may not have a service of the foregoing VPN instances, and the occupation of system resources on a receiver PE router is excessively large. The same problem occurs on the source PE configuring the receiver VPN multicast instance.
Additionally, if VPN multicast instances of a plurality of remote PEs for a multicast stream of the source VPN multicast instance need to be received, since each receiver VPN needs to transfer the multicast stream through its own multicast tunnel, a public network performs encapsulation and replication in a Share-Group multicast distribution tree of a plurality of receiver VPNs, and meanwhile a plurality of traffic is forwarded for a piece of multicast data, thereby increasing the network load.